1. Field of the Invention
The present invention relates to a power-generation control apparatus that controls power-generation operation of an in-vehicle electric rotating machine mounted in a vehicle.
2. Description of the Related Art
To date, an electric power generator that serves as an in-vehicle electric rotating machine mounted in a vehicle such as an automobile has been controlled by a voltage adjuster (regulator) in such a way that the generated voltage becomes constant regardless of the condition of the vehicle. However, in recent years, there has been employed a technology that variably controls a voltage to be generated by an electric power generator, in accordance with the traveling condition of a vehicle, the conditions of electric loads, the condition of a battery, or the like, in order to protect the environment, to improve the gasoline mileage, to raise the drivability, or the like. According to the foregoing technology, for example, the power-generation control is performed in such a way that, when a vehicle is accelerated, an in-bound power generation voltage command value for an electric power generator is set to a low value so that load torque for the engine is reduced, and when the vehicle is decelerated or when the accelerator pedal is released, the voltage to be generated is sharply raised so that the power generation is actively performed.
On the other hand, a widely spread gasoline engine is very powerless in a low rotation speed region and is characterized in that the torque responsiveness thereof is considerably low, compared to the responsiveness of the power-generation torque of the electric power generator mounted in the engine. Accordingly, in order to stabilize the rotation of the engine, there has been performed a so-called load-responsive control in which, even in the case where the electric load on the electric power generator drastically increases, the output of the electric power generator is raised not drastically but gradually.
Moreover, as an in-vehicle power generator control apparatus for controlling the output voltage of an in-vehicle power generator that charges a battery, there has been proposed a power-generation control apparatus (e.g., refer to Japanese Patent Application Laid-Open No. 2002-315221) in which there are included a duty ratio detection means that detects the duty ratio of a pulse signal as a command signal inputted from an external control apparatus, a load-responsive control means that suppresses increase in the magnetic-field current of the in-vehicle power generator, and a nullification control means that nullifies the operation of the load-responsive control means when a duty ratio detected by the duty ratio detection means falls within a predetermined range; by making the external control apparatus set the duty ratio of the pulse signal to a value within the predetermined range, it is determined whether or not the load-responsive control is required, and then by concurrently utilizing generated-voltage control and the load-responsive control in such a way that these controls compensate their shortcomings each other, the stabilization of the rotation of the engine and reduction of fuel costs are achieved.
A power-generation control apparatus, for an electric rotating machine, that performs suppression control of a power-generation amount through conventional load-responsive control operates even in a rapid power-generation period, such as a vehicle-speed deceleration period, during which electric power is actively generated; therefore, there has been a problem that a sufficient power-generation amount cannot be secured in a short-time rapid power-generation period. In the case of the conventional power-generation control apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-315221, by regarding, as a rapid-charging required period, only the period during which the duty ratio as a present generated-voltage command is within the predetermined range, a power-generation amount suppression means is nullified. Accordingly, in a period during which the duty ratio is not within the predetermined range, the power-generation amount suppression means cannot be nullified; therefore, there has been a problem that fine control, of the power-generation amount, which complies with demands cannot be performed.